A gun is a normally tubular weapon or another device designed to discharge projectiles or other materials. The projectile may be solid, liquid, gas or energy and even may be free, as with bullets and artillery shells, or captive as with Taser probes and whaling harpoons.

The means of projection varies according to design but is usually affected by the action of gas pressure, either produced through the rapid combustion of a propellant or compressed and stored by mechanical means, operating on the projectile inside an open-ended tube in the fashion of a piston. The confined gas accelerates the projectile down the length of the tube imparting sufficient velocity to sustain the projectile’s travel once the action of the gas ceases at the end of the tube or muzzle. Alternatively, acceleration via electromagnetic field generation may be employed in which case the tube may be dispensed with and a guide rail substituted.

The first devices identified as guns appeared in China around 1000AD, and by the 12th century the technology was spreading through the rest of Asia, and into Europe by the 13th century. The origin of the English word gun is presently considered to derive from the name given to a particular historical weapon.

Domina Gunilda was the name given to a remarkably large ballista, a mechanical bolt throwing weapon of huge size, mounted at Windsor Castle during the 14th century. This name in turn may have derived from the Old Norse woman’s proper name Gunnhildr which combines two Norse words referring to battle.

In any case the term gonne or gunne was applied to early hand-held firearms by the late 14th century or early 15th century.

Lego’s are probably the most famous toys manufactured by The Lego Group, a privately held company based in Billund, Denmark. The company’s flagship product, Lego, consists of colorful interlocking plastic bricks and an accompanying array of gears, mini figures and many other parts. Lego bricks can be assembled and connected in many ways, to construct such objects as vehicles, buildings, and even working robots. Anything constructed can then be taken apart again, and the pieces used to make other objects.

Lego began manufacturing interlocking toy bricks in 1949. Since then a global Lego subculture has developed, supporting movies, games, competitions, and six themed amusement parks. As of 2013, around 560 billion Lego parts had been produced.

The Lego Group began in the workshop of Ole Kirk Christiansen, a carpenter from Billund, Denmark, who began making wooden toys in 1932. In 1934, his company came to be called “Lego”, from the Danish phrase leg godt, which means “play well”. It expanded to producing plastic toys in 1947. In 1949 Lego began producing, among other new products, an early version of the now famous interlocking bricks, calling them “Automatic Binding Bricks”.

These bricks were based in part on the KiddicraftSelf-Locking Bricks, which were patented in the United Kingdom in 1939 and then there released in 1947. Lego modified the design of the Kiddicraft brick after examining a sample given to it by the British supplier of aninjection-molding machine that the company had purchased.

Cat play and toys incorporates predatory games of “play aggression”. Cats’ behaviors when playing are those similar to hunting behavior. These activities allow kittens and younger cats to grow and acquire cognitive and motor skills, and also to socialize with other cats. Cat play behavior can be either solitary or social. They can play with a multitude of toys ranging from strings, to small furry toys resembling what would be prey (e.g. mice) to plastic bags.

Since cats are predators, nearly all cat games are predatory games.

Prey is fearful of predators. Predators often encounter prey that attempt to escape predation. Prey that moves towards the cat with confidence may be exhibiting an aggressive defensive posture. Cats often play with toys that behave more like fearful prey trying to escape than toys that mimic a more confrontational prey.

Success rate is important in play. A cat that catches its prey every time soon gets bored, and a cat that never gets it just loses interest. The ideal hunting success rate is around 1 in 3 to 1 in 6. Capturing prey at this rate generally maximize a cat’s interest in the game.

Play is about predation, and a highly excited cat can cause minor injuries in the excitement of the moment. With most cats, it is wise to keep playthings at least 20 cm (8″) away from fingers or eyes, and avoid encouraging a cat to eat inedible toys.

Railway modelling (UK, Australia, Ireland and Canada) or model railroading (US and Canada) is a hobby in which rail transport systems are modelled at a reduced scale, or as realistically as possible in 3D utilizing self-defining graphical objects in V-scale or Virtual scale modeling rendered in a virtual world by a compatible graphics engine.

The scale models include locomotives, rolling stock, streetcars, tracks, signalling, and roads, buildings, vehicles, model figures, lights, and features such as streams, hills and canyons. In a physical model, the objects are built of materials, in V-scale by a combination of scripts, sounds, rules, textures and polygon meshes using graphics modeling software such as Gmax or Blender. Both physical and graphics modeling take painstaking effort, knowledge and special skills. Many Model Railroad Clubs utilize both technologies in group activities.

The earliest model railways were the ‘carpet railways’ in the 1840s. Electric trains appeared around the start of the 20th century, but these were crude likenesses. Model trains today are more realistic. Today modellers create model railway / railroad layouts, often recreating real locations and periods in history.

Involvement ranges from possession of a train set to spending hours and large sums on a large and exacting model of a railroad and the scenery through which it passes, called a “layout”. Hobbyists, called “railway modellers” or “model railroaders”, may maintain models large enough to ride.

A map is a visual representation of an area – a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes.

Most of the maps are static two-dimensional, geometrically accurate (or approximately accurate) representations of three-dimensional space, while others are dynamic or interactive, even three-dimensional. Although usually used to depict geography, maps may represent any space, real or imagined, without regard to context or scale; e.g. brain mapping, DNA mapping and extraterrestrial mapping.

Cartography or map-making is the study and practice of crafting representations of the Earth upon a flat surface, and a person who makes maps is called a cartographer.

Road maps are perhaps the most widely used maps today, and form a subset of navigational maps, which also include aeronautical and nautical charts, railroad network maps, and hiking and bicycling maps. In terms of quantity, the largest number of drawn map sheets is probably made up by local surveys, carried out by municipalities, utilities, tax assessors, emergency services providers, and other local agencies. Many national surveying projects have been carried out by the military, such as the British Ordnance Survey (now a civilian government agency internationally renowned for its comprehensively detailed work).

In addition to location information maps may also be used to portray contour lines indicating constant values of elevation, temperature, rainfall, etc.

A Furby (plural Furbys or Furbies) is an electronic robotic toy resembling a hamster or owl-like creature which went through a period of being a “must-have” toy following its launch in the holiday season of 1998, with continual sales until 2000. Over 40 million Furbies were sold during the three years of its original production, with 1.8 million sold in 1998, and 14 million in 1999. Its speaking capabilities were translated into 24 languages.

Furbies were the first successful attempt to produce and sell a domestically-aimed robot. A newly purchased Furby starts out speaking entirely Furbish, the unique language that all Furbies use, but is programmed to start using English words and phrases in place of Furbish over time. This process is intended to resemble the process of learning English.

In 2005, new Furbies were released, with voice-recognition and more complex facial movements, and many other changes and improvements. The Emoto-Tronic Furbies (Furby, Furby Baby, and Funky Furby) continued to be sold until late 2007, when these toys became extremely rare. An updated Furby is being sold as of September 2012 for the holiday season.

A rubber band (in some regions known as a binder, an elastic or elastic band, alackey band, laggy band, lacka band, or gum band) is a short length of rubber and latex formed in the shape of a loop and is commonly used to hold multiple objects together. The rubber band was patented in England on March 17, 1845 by Stephen Perry.

Rubber bands are made by extruding the rubber into a long tube to provide its general shape, putting the tubes on mandrels, curing the rubber with heat, and then slicing it across the width of the tube into little bands.

While other rubber products may use synthetic rubber, most rubber bands are primarily manufactured using natural rubber because of its superior elasticity.

Natural rubber originates from the latex of the rubber tree. Natural rubber is made from latex which is acquired by tapping into the bark layers of the rubber tree. Rubber trees belong to the spurge family (Euphorbiaceae) and live in warm, tropical areas. Once the latex has been “tapped” and is exposed to the air it begins to harden and become elastic, or “rubbery.” Rubber trees only survive in hot, humid climates near the equator and so the majority of latex is produced in the Southeast Asian countries of Malaysia, Thailand and Indonesia.

A shack is a type of small, often primitive shelter or dwelling. The word may derive from the Nahuatl (Aztec) word xahcalli or “adobe house” by way of Mexican Spanish xacal/jacal, which has the same meaning as “shack”. It was a common usage among people of Mexican ancestry throughout the U.S. southwest and was picked up by speakers of American English.

An alternative etymology is that shack derives from teach, pronounced chaċ, meaning “house” in Irish Gaelic, which was absorbed into American English from the 1880s onwards. Similarly shanty may have derived from the Gaelic seantigh, prounced shan-tí, meaning “old house”, at a time when Irish migrants lived in New York’s tenements.

It is possible that up to a billion people worldwide live in shacks. Fire is a significant hazard in tight-knit shack settlements. Shack settlements are also sometimes known as slums or shanty towns.

In amateur radio jargon, a shack refers to the place where an amateur radio operator’s radio sending and receiving apparatus is located and operated. The term originally meant that part of a ship where the radio apparatus was located and operated. This is the inspiration for the name ‘RadioShack’.

In military aviation jargon, a “shack” refers to a successful, direct hit on a ground target.

Bus stops are often referred to as “shacks” by commuters and the common passerby because some bus stops have roofs on top of the stops for shade and protection from the rain.

Teeth of humans are small, calcified, hard, whitish structures found in the mouth. They function in mechanically breaking down items of food by cutting and crushing them in preparation for swallowing and digestion. The roots of teeth are embedded in the maxilla (upper jaw) or the mandible (lower jaw) and are covered by gums. Teeth are made of multiple tissues of varying density and hardness.

Teeth are among the most distinctive (and long-lasting) features of mammal species. Humans, like other mammals, are diphyodont, meaning that they develop two sets of teeth. The first set (also called the “baby”, “milk”, “primary”, and “deciduous” set) normally starts to appear at about six months of age, although some babies are born with one or more visible teeth, known as neonatal teeth. Normal tooth eruption at about six months is known as teeth ingand can be painful.

Dental trauma refers to trauma to the face, mouth, and especially the teeth, lips and periodontium. The study of dental trauma is called dental traumatology.

Dental anatomy is a field of anatomy dedicated to the study of tooth structure. The development, appearance, and classification of teeth fall within its field of study, though dental occlusion, or contact among teeth, does not. Dental anatomy is also a taxonomic science as it is concerned with the naming of teeth and their structures. This information serves a practical purpose for dentists, enabling them to easily identify teeth and structures during treatment.

A Christmas tree is a decorated tree, usually an ever green conifer such as pine or fir, traditionally associated with the celebration of Christmas. An artificial Christmas tree is an object made to resemble such a tree, usually made from polyvinyl chloride (PVC).

The tree was traditionally decorated with edibles such as apples, nuts or dates. In the 18th century, it began to be illuminated by candles, which with electrification could also be replaced by Christmas lights. Today, there is a wide variety of traditional ornaments, such as garland, tinsel, and candy canes. An angel or star may be placed at the top of the tree, to represent the host of angels or the Star of Bethlehem from the Nativity.

The custom of the Christmas tree developed in early modern Germany with predecessors that can be traced to the 16th and possibly the 15th century. It acquired popularity beyond Germany during the second half of the 19th century. The Christmas tree has also been known as the “Yule-tree”, especially in discussions of its folkloristic origins.

While it is clear that the modern Christmas tree originates in Renaissance and early modern Germany, there are a number of speculative theories as to its ultimate origin. Its 16th-century origins are sometimes associated with Martin Luther.

It is frequently traced to the symbolism of evergreen trees in pre-Christian winter rites, especially with the story of the Donar Oak and Saint Boniface.